plow or plough, agricultural implement used to cut furrows in and turn up the soil, preparing it for planting. The plow is generally considered the most important tillage tool. Its beginnings in the Bronze Age were associated with the domestication of draft animals and the increasing demand for food resulting from the rise of cities. The plow is depicted on Egyptian monuments, mentioned in the Old Testament, and described by Hesiod and Vergil. The early plow consisted simply of a wooden wedge, tipped with iron and fastened to a single handle, and a beam, which was pulled by men or oxen. Such implements were capable of breaking but not of inverting the soil. The plow evolved gradually until c.1600, when British landlords attempted greater improvements. The first half of the 18th cent. saw the introduction into England of the moldboard, a curved board that turns over the slice of earth cut by the share. Important improvements in design and materials were made in the early part of the 19th cent. They included streamlined moldboards, replaceable shares, and steel plows with self-scouring moldboards. Standardized by 1870, the modern moldboard plow has been improved by various attachments, e.g., the colter, a sharp blade or disk that cuts the ground in advance of the share. In 19th-century America horses largely replaced oxen for drawing plows. Tractors now supply this power in most developed parts of the world. With more powerful tractors, larger plows have come into use. Among the various types of plows in use today are the reversible two-way plow for contour plowing; listers and middlebusters, which prepare shallow beds; the disk plow, whose revolving concave disks are useful in working hard or dry soil; the rotary plow, with an assembly of knives on the shaft that mix the surface growth with the soil; and the chisel plow, with points mounted on long shanks to loosen hard, dry soils and shatter subsurface hardpan. The plow often symbolizes agriculture, as in the great seals of New Jersey, Pennsylvania, Tennessee, and other states.
See publications of the U.S. Dept. of Agriculture; C. Culpin, Farm Machinery (12th ed. 1992).